1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly, it relates to a method of fabricating a semiconductor device formed with a conductive member in an opening.
2. Description of the Prior Art
In relation to multilevel interconnections recently employed for a highly integrated semiconductor device, reduction of resistance of a wire-to-wire contact (via contact) and improvement of reliability of the wires are required.
Further, the degree of integration of the semiconductor device is increasingly improved and hence the diameter of a contact hole (regarded as a synonym for a via hole) must be reduced. When the diameter of the contact hole is reduced, however, it is difficult to deposit a wiring material in the contact hole with a sufficient thickness.
High-temperature sputtering has been generally employed as one of methods of embedding wiring materials. The high-temperature sputtering is disclosed in xe2x80x9cHigh Temperature Aluminum Planarization Process for ULSI Devicesxe2x80x9d, Jun. 7-8, 1994 VMIC Conference, 1994 ISMIC-103/94-0374, pp. 374 to 376, for example. According to this high-temperature sputtering, filling of a contact hole and formation of a wire can be performed through a single step by sputtering a wiring material while heating a wafer to a high temperature. Thus, the number of fabrication steps for a semiconductor device can be reduced for suppressing the fabrication cost. The wiring material is most generally prepared from an aluminum alloy.
As the diameter of the contact hole is reduced following improvement in degree of integration of the semiconductor device, it is difficult to fill up the contact hole through the conventional high-temperature sputtering. More specifically, an interlayer dielectric film discharges moisture and hydroxyl groups into the contact hole as a gas, to disadvantageously increase pressure in the contact hole and inhibit flowability of the aluminum alloy. Such disadvantage remarkably takes place as the diameter of the contact hole is reduced. Consequently, excellent electric characteristics cannot be attained.
An object of the present invention is to provide a method of fabricating a semiconductor device capable of attaining an excellent embedding characteristic also when an opening (contact hole/via hole) has a small diameter.
Another object of the present invention is to improve wettability of a conductive member embedded in the opening in the aforementioned method of fabricating a semiconductor device.
Still another object of the present invention is to prevent the conductive member from disconnection in the aforementioned method of fabricating a semiconductor device.
A method of fabricating a semiconductor device according to an aspect of the present invention comprises steps of forming an interlayer dielectric film having an opening, forming a first conductive member in the opening by sputtering, and performing first heat treatment at a temperature capable of reducing the quantity of moisture and hydroxyl groups in the interlayer dielectric film in advance of formation of the first conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the first heat treatment is previously performed at the temperature capable of reducing the quantity of moisture and hydroxyl groups in the interlayer dielectric film in advance of formation of the first conductive member so that the interlayer dielectric film has a small quantity of moisture and hydroxyl groups when the first conductive member is embedded in the opening, whereby the embedding characteristic of the first conductive member is improved. Consequently, electric characteristics of a contact part can be improved also when the opening has a small diameter.
Preferably, the method of fabricating a semiconductor device according to the aforementioned aspect further comprises a step of forming a second conductive member containing titanium in the opening after performing the first heat treatment in advance of formation of the first conductive member. In this case, wettability of the first conductive member is improved. Thus, the embedding characteristic of the first conductive member with respect to the opening can be improved, whereby an excellent contact characteristic can be attained also when the opening has a small diameter. In this case, the second conductive member may be formed by a multilayer film of a titanium layer and a titanium nitride layer.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of forming the first conductive member preferably includes a step of performing the sputtering at a low temperature and thereafter performing the sputtering at a high temperature thereby forming the first conductive member. In this case, wettability of the first conductive member is improved. Thus, the embedding characteristic of the first conductive member with respect to the opening can be improved, whereby an excellent contact characteristic can be attained also when the opening has a small diameter.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the interlayer dielectric film preferably includes an organic SOG film. Thus, flatness of the interlayer dielectric film is so improved that the first conductive member formed on the upper surface of the interlayer dielectric film can be prevented from disconnection. In this case, the method of fabricating a semiconductor device preferably further comprises a step of introducing an impurity into the organic SOG film in advance of formation of the first conductive member. Thus, the organic SOG film containing the introduced impurity discharges a small quantity of gas of moisture and hydroxyl groups also when the same is kept at a high temperature, whereby the embedding characteristic of the first conductive member with respect to the opening can be further improved. Consequently, an excellent contact characteristic can be attained also when the opening has a small diameter.
In this case, the method of fabricating a semiconductor device preferably further comprises a step of performing second heat treatment on the organic SOG film containing the introduced impurity in advance of formation of the first conductive member. The number of dangling bonds is reduced in the organic SOG film containing the introduced impurity due to this structure. Thus, hygroscopicity of the organic SOG film containing the introduced impurity is further reduced, to allow permeation of a smaller quantity of moisture. Consequently, the organic SOG film discharges a smaller quantity of gas of moisture and hydroxyl groups, whereby the embedding characteristic of the first conductive member with respect to the opening can be further improved.
A method of fabricating a semiconductor device according to another aspect of the present invention comprises steps of forming an interlayer dielectric film having an opening, forming a first conductive member in the opening by sputtering, and performing first heat treatment at a temperature exceeding the sputtering temperature for the sputtering in advance of formation of the first conductive member.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the first heat treatment is previously performed at a temperature exceeding the sputtering temperature for the sputtering in advance of formation of the first conductive member so that the quantity of moisture and hydroxyl groups in the interlayer dielectric film is reduced when the first conductive member is embedded in the opening by sputtering, whereby the embedding characteristic of the first conductive member is improved. Consequently, electric characteristics of a contact part can be improved also when the opening has a small diameter.
Preferably, the method of fabricating a semiconductor device according to the aforementioned aspect further comprises a step of forming a second conductive member containing titanium in the opening after performing the first heat treatment in advance of formation of the first conductive member. In this case, wettability of the first conductive member is improved. Thus, the embedding characteristic of the first conductive member with respect to the opening can be improved, whereby an excellent contact characteristic can be attained also when the opening has a small diameter. In this case, the second conductive member may be formed by a multilayer film of a titanium layer and a titanium nitride layer.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the step of forming the first conductive member preferably includes a step of performing the sputtering at a low temperature and thereafter performing the sputtering at a high temperature thereby forming the first conductive member. In this case, wettability of the first conductive member is improved. Thus, the embedding characteristic of the first conductive member with respect to the opening can be improved, whereby an excellent contact characteristic can be attained also when the opening has a small diameter.
In the method of fabricating a semiconductor device according to the aforementioned aspect, the interlayer dielectric film preferably includes an organic SOG film. In this case, flatness of the interlayer dielectric film is so improved that the first conductive member formed on the upper surface of the interlayer dielectric film can be prevented from disconnection. In this case, the method of fabricating a semiconductor device preferably further comprises a step of introducing an impurity into the organic SOG film in advance of formation of the first conductive member. Thus, the organic SOG film containing the introduced impurity discharges a small quantity of moisture and hydroxyl groups also when the same is kept at a high temperature, whereby the embedding characteristic of the first conductive member with respect to the opening can be further improved. Consequently, an excellent contact characteristic can be attained also when the opening has a small diameter.
In this case, the method of fabricating a semiconductor device preferably further comprises a step of performing second heat treatment on the organic SOG film containing the introduced impurity. The quantity of dangling bonds is reduced in the organic SOG film containing the introduced impurity due to this structure. Thus, hygroscopicity of the organic SOG film containing the impurity is further reduced, to allow permeation of a smaller quantity of moisture. Consequently, the organic SOG film discharges a smaller quantity of gas of moisture and hydroxyl groups, whereby the embedding characteristic of the first conductive member with respect to the opening can be further improved.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.